(arrivé) "cinq minutes en retard"

Question

Shown as valid option, but my answer was marked with pink (error?) with the alternative "avec cinq minutes de retard" in blue (preference check mark?) although I received credit for the question

Answer

Bonjour Robert,
It has been a while since I have had that occur on my response to a question.  It is my understanding that the program considers your answer correct, hence the pink, but it considers another response to be the correct response.  (Aren't computer programs wonderful since they tend to view response in a «black and white» context)  
I think that anyone who has studied French for any length of time, or English for that matter, know that there are usually multiple ways to respond or word phrases with the same or similar meaning, typically known as syntax.  Even with one word responses, there is usually more than one word that will suffice, i.e. manger, avaler, dévorer, déjeuner, dîner, se nourrir, se sustenter, etc. 
J'espère que cela vous aiderait.
Bonne chance.
Ron

Answer

I have the same question.  What am I missing?